Film mount and mask for a pair of panoramic stereoscopic images

ABSTRACT

A film mount and mask for a panoramic stereoscopic camera in which processed film strip has stereoscopic pairs of film frames cut and mounted in a holder providing a mask for each frame and means comprising a boss provided for each film frame in the mount to register with a notch in the film for positioning purposes, and to prevent the film frame from moving towards either extremity when heated in a projector, each film frame being held in a cylindrical plane by means of a mask, with means formed into the mount to accept either clips, or plastic feet in the case of a plastic mask, to secure the film frames tight against the curved focal plane formed in the mount, said plane being identical as to focal radius with the curved film bed in the panoramic stereoscopic camera in which the film was exposed.

United States Patent 1 Bernier 1 3,723,904 1 Mar. 2'7, 1973 [54] FILMMOUNT AND MASK FOR A PAIR OF PANORAMIC STEREOSCOPIC IMAGES [75]Inventor: Robert V. Bernier, Saugus, Calif.

[73] Assignee: TRW Inc., Cleveland, Ohio [22] Filed: Oct. 13, 1971 211Appl. No.: 188,896

[52] US. Cl ..40/l52 [51] Int. Cl ..G09i' 1/12 [58] Field0iSearch....40/10, 152,158,158 B, 63 A,

[56] References Cited 9 UNITED STATES PATENTS 2,803,077 8/1957Baireuther ..40/l52 2,968,108 l/196l Knox ...40/l52 2,971,282 2/1961Petrey ..40/152 3,424,511 H1968 Ratliff i ..350/135 3,649,099 3/1972Furuoka ..350/135 -III/IIIIIIl/lllllnalum Primary Examiner-Robert W.Michell Assistant Examiner-Wenceslao J. Contreras Att0rney-Milton E.Gilbert [57] ABSTRACT A film mount and mask for a panoramic stereoscopiccamera in which processed film strip has stereoscopic pairs of filmframes cut and mountedin a holder providing a mask for each frame andmeans comprising a boss provided for each film frame in the mount toregister with a notch in the film for positioning purposes, and toprevent the film frame from moving towards either extremity when heatedin a projector, each film frame being held in a cylindrical plane bymeans of a mask, with means formed into the mount to accept eitherclips, or plastic feet in the case of a plastic mask, to secure the filmframes tight against the curved focal plane formed in the mount, saidplane being identical as to focal radius with the curved film bed in thepanoramic stereoscopic camera in which the film was exposed.

10 Claims, l7'Drawing Figures Patented March 27, 1973 3,723,904

2 Sheets-Sheet l INVENTOR.

ROBERT V. BERNIER Maw ATTORNEY Patented March 27, 1973 3,723,904

2 Sheets-Sheet f;

284 FIG-I5 FIG I6 INVENTOR.

ROBERT V BERN IER ATTORNEY FILM MOUNT AND MASK FOR A PAIR OF PANORAMICSTEREOSCOPIC IMAGES STATE OF PRIOR ART DRAWINGS FIG. 1 is a perspectiveview of the film mount of the invention showing two panoramicstereoscopic film frames mounted and registered into position;

FIG. 2 is a rear view of the film mount of the invention shown in FIG.1;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2; 7

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 2;

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 2;

FIG. 6 is a perspective view of a film frame and mask;

FIGS. 7,8 and 9 are partial cross-sectional views through a film mountshowing the assembly of a mask and film frame therein;

FIG. 9a is 'a detail of the sprocket hole structure of the film strip.

FIG. 10 is a perspective view of the mask of FIG. 6, slightly modified;

FIG. 1 1 is a perspective view ofa modified mask;

Flg. 12 is a side view of the mask of FIG. 11 with a partialcross-section taken along the plane passing through ribs 310 and 304;

FIG. 13 is a rear view of the mask of FIG. 11;

FIGS. 14 and 15 are partial cross-sectional views for checking on theuniformity of cross-section of the plastic thickness. Additionally, therecessed area 22 is in the nature of a step down from the surface 4, andtogether with the further step" 24 preventing occulating of the line ofsight in the inner areas of the film. The latter would occur whenviewing the extremities of the film ifa protruding portion of the mountwere seen.

through a film mount showing the assembly of the mask of FIG. 11therein; and

FIG. 16 is a schematic representation of operational aspects of the filmmount of the invention.

DETAILED DESCRIPTION OF INVENTION The film mount is generally shown inFIG. 1, and comprises a body 2, preferably made of plastic, and havingan upwardly extending surface 4 to enable handling without touching theframes. Indented areas 6 and 8 are provided ,on the back of the surface4 (see FIG. 2) towhich may be affixed identification labels if desired.

A pair of window openings 10, and 12, are provided to receive the leftand right, respectively, film frames of a stereo pair or pair of stereoimages. The curvature of the window portions (see especially FIG. 3)10,12 are made identical, as to focal radius, with the curved film bedof the panoramic stereoscopic camera in which the exposures were made.For this purpose the curved seats 14 and 16 (see FIG. 1) are formedabove' and below the window opening 10, for example, andv the similarcurved seats 18 and 20 are provided for the window 12. Recess 22 isformed as a flat surface to serve as a means Similar stepped portionsare provided .(not numbered) on the rear of the body 2 to permit nestingofa plurality of the mounts 1. Steps 26 are provided on the front of themount also for nesting alignment.

The front of the mount is provided with the dim-,-

pied areas 28 and 30 which register with a retaining means in astereoscopic panoramic viewer (e.g. springs) to hold the film mount inposition within the viewer. The mount is thus accurately registered andis held by a means bearing against one side of the mount.

The central portion of the body 2 is provided at the rear with upper,36, and lower, 34, positioning ledges (see especially FIG. 5). On theleft side at the rear of the body 2 (as viewed in FIG. 2), there isprovided a continuous U-shaped ledge 38, and at the right side at therear of the body 2 there is provided the similar ledge 40. The bottomportion of these ledges align the mount in. correct horizontal position,and the face of each of these ledges serves to align the mountvertically in a vertical plane, they fit up against the vertical facesor surfaces of the mount holder in the panoramic viewer. As shown moreclearly in FIG. 3, the ledges 38 and 40 are formed in a re-entrantmanner, i.e. are spaced from the main portion ofthe body 2 to form thechannels or grooves 42 and 44, respectively. A groove 46 is formed inthe central portion of the body 2 as shown in'FIG. 5. These grooves 42,44 and 46 serve to accommodate film mask retaining clips which arediscussed hereinafter.

The upper seat 14 of the window 10 has formed thereon a depending boss48, and the upper seat 18 of the window.12 similarly has formed thereonthe depending boss 50, both bosses being otherwise identical. Thesebosses are used to register with notches which have been previously cutinto the film, and also with similar notches formed in the film maskdescribed hereinafter. As shown clearly in FIG. 4 theupper part of therail 14 is recessed so that the film is permitted to lie flat againstthe rail. The reason for'such recessing is apparent from a considerationof the molding process, wherein the plastic may be formed with aprotruding radius" at the top and bottom, respectively, of the upper andlower seats, so as to prevent the film frame from lying flat against thedesired surface (i.e. it might be pressed outwardly by a radius). Thisconstruction results in the formation of the upper rails 52 and 54, andlower rails 56 and 58 (see FIGS. 2 and 4) against which the film framewill be seated. These rails are also undercut, as shown at 60, withrespect to rail 52; and as shown at 62, with respect to rail 56. Theseundercuts serve to eliminate radiuses that might otherwise occur in themolding of the plastic at the top edge and the bottom edge of the filmrecess. The film is thus permitted to lie flat against the rails.

Turning now to FIG. 6 there is explained the means for positioning thepreviously cut film frame strips on the rails and their retention inposition by a resilient member, which could be plastic or metallic. Sucha resilient member is shown generally as 64, and could be of springmaterial and is of a curved configuration, of a radius le s 5 than thatinto which it will be constrained after assembly or installation intothe mount.

The constraint is provided by the use of clips for retention whichserves to apply pressure to the film at its central area since theresilient member or frame member such as 64 tends to straighten out, andin attempting to do so it bears more strongly upon the central area ofthe film.

Unless the pair of stereo images or film frames are mounted at thecorrect distance apart from one another, and are properly masked,satisfactory relief effects cannot be obtained. Therefore, with respectto the mask, and in order to obtain correct three dimensional viewing,it is necessary to fix a reference plane such that all objects frominfinity to the closest object will appear in their correct spatialrelationship to such reference plane. It is desired that this referenceplane should bear the same relationship to the objects in the photographthat an open window or veranda bears to the scene beyond. Thus, thestereo effect on a panoramic basis is best obtained if the images are somounted that, when viewed, the observer appears to be looking through averanda at the three dimensional objects comprising the scene. The frameor marginal edges of the openings in the left eye and right eye masksshould have their corresponding vertical edges at a distance apartslightly less than 65 mm (the interaxial distance of the lenses in apreferred form of panoramic viewer, as well as the average interpupilarydistance of the eyes). This distance, in a quantitative sense, should beless than the distance apart (in the two stereoscopic images) ofclose-up images. In this manner can the closeup objects spatially appearbeyond the masked opening.

When the film frames are mounted in the film mount means are providedfor insuring that the film frames are mounted at a distance apart whichis approximately the same as when they were when taken in the camera,i.e. identical infinity image points on the two stereo film frames arelocated at a distance apart which is equal to the interaxial distance ofthe viewer lenses as well as what would be the average interpupilarydistance. Thus, when viewing the mounted stereo film pairs, the sightlines of the eyes must diverge to a parallel condition to fuse oninfinity images. This condition of the eyes tells the brain that theobject being looked at is in fact at infinity. Once the film frames arecorrectly mounted so that infinity objects are made to appear atinfinity, as described above, all other objects photographed at lesserdisances from the camera will also appear, when viewed, at their properdistances. This is so because the camera lenses will have automaticallycaused the respective disparate images of objects at different distancesto be displaced towards each other on the film an amount directlyproportional to the various distances to the objects. When viewing themounted frames the eyes will need to converge to fuse on the differentsets ofdisparate images. The amount of this convergence gives the brainthe data it needs to cause objects to appear, when viewed, in space attheir correct relative distances. Correct positioning of the film framesin the mount is accomplished by placing a registration notch in the filmstrip 70 which is centered on the central axis of the film frame image.It is noted that the central axis of the film frame image does notalways fall exactly between perforations. As shown in FIGS. 6 and 9A,the film strip is provided with the normal sprocket perforations 72 atits upper and lower edges. Along the upper edge of the strip 70 isplaced a fiducial mark 74, which desireably is placed there during theexposure of the film in the camera. The vertical edge 78 of the fiducialmark 74 indicates the exact central axis of the film frame image and isaligned when previously cutting the notch 76, so that the center line ofthe notch 82 also falls at the exact central axis of the film frameimage. The slanting leg of the fiducial mark 74 indicates whether thefilm frame image on which it appears is a right eye or a left eye image.As shown in FIG. 9A the slanting leg 80 of the fiducial mark 74 slantsaway from the vertical leg 78 to the right. Thus this would indicatethat this particular film frame image would be a right eye image andshould be mounted in the right hand side of the film mount. When readingthe direction of slant of the fiducial mark the film strip should beheld with the emulsion side of the film facing away from the eyes,and/or the film strip should be held such that the film image appears toagree with the subject matter photographed left for right and top forbottom.

As mentioned hereinbefore, the mount of the invention is so constructedas to provide a reference plane formed visually as a spatial window.This is brought about by providing for an opening in each film maskwhich is displaced inwardly towards the center of the mount by an amounta little greater than the inward displacement which the eyes mustaccommodate in viewing close-up objects. A shown in FIG. 6 the resilientmember, frame or mask 64 is provided with upper 66, and lower 68, railswhich are provided with notches 67 and 69 on their respective outeredges. For accomplishing the purposes abovementioned only one notch needbe provided, however, it is to be understood that it is desireable tointerchange and reuse the masks with different film frames, and thus themask 64 could be inverted for use on the opposite side of the mount I.One of the notches (whichever one is oriented at the top) 67, 69 engageseither the boss 48 or 50 as discussed hereinafter. Such registration ofnotch and boss serves to retain the mask 64 in fixed position within thewindow 10 or 12, upon assembly therein. The two windows 10, 12 aredisplaced inwardly towards the center of the mount with respect to themount centerline. This is accomplished by making the outer side of themask wider than the inner side, thus shifting the actual center line ofthe window opening when the mask is mounted therein. With a pair ofmasks containing film frames of a stereo pair mounted in the mount 1,the wider edges of the masks are on the outside of the mount and thenarrower edges of the masks are located towards the center of the mount.This serves to displace the window opening of each mask inwardly withrespect to the images on each of the film frames. As shown in FIG. 6, inaddition to the upper and lower rails, the mask 64 is provided with siderails. The left oriented side rail as viewed in FIG. 6 is formed withthe curved portion 88 (which is a continuation of the curvature of theupper and lower rails) and a bent over straight portion or flange 84.The right oriented side rail is similarly formed with the curved portion90 and the flange 86. Although not clearly shown in FIG. 6, it isintended that the left rail be wider than the right rail of the mask 64.

In order to affix and retain the mask and film strip in the mount, aseries of clips 92, 94, 96 and 98 are provided. These clips areidentically formed and clip 92 is described hereinafter, it beingunderstood that the other clips haveidentical features. Clip 92 isformed with the bent-over V-shaped spring portion 100 and a straightportion 102. The positioning of the parts upon assembly is more clearlyshown in FIG. 9, wherein the clip 92 is shown as snapped into positioninto the channel 42, with the spring portion 100 bearing the innersurface of the ledge 38 and slightly gauging or displacing it for betterfrictional retention. The flange 84 ofthe mask 64 is retained inposition by the clip portion 102 bearing against it and seating itagainst the body 2. As shown in FIGS. 7 and 8, the mask 64 is held atits other side by the clip 96, which snaps into the channel 46, FIG. 7showing the clips only placed into the channels, and FIG. 8 showing theclips pushed fully into place. In this manner the film frame is broughtinto close contact and retained against the rails 66 and 68, especiallyat the central portion thereof so that when viewed in a viewer (and thussubjected to the heat of an illuminating source) the film will notbuckle away from the rails.

Some of the theoretical considerations discussed above can be morereadily understood with reference to FIG. 16, which is a schematicrepresentation of the spatial effects created by the mount of theinvention when placed into a viewer. An image of a window, per mitting atrue three dimensional viewing, is created by means of a referencepoint. The vertical edges of the scene appearing on the stereo filmimage pair are not seen always since in a viewer one would have to tryto look around corners" to view such edges. Without vertical edgeswithin the field of view, other reference points must be provided, andthese are accomplished by the use of novel ribs or notches on the mask.As shown in FIG. 16, the human eyes are represented as 104 and 106, withthe lines of sight passing through the lenses 108 and 110, respectively,and through the plane 112 of the film frames (the doubly curvedplanewhen the two masks are properly mounted in the mount). As is wellunderstood, the lenses of the viewer serve to aid the eyes to come to afocus on the relatively close proximity (to the eyes) of the film planeand mask 112. The latter serves as the plane ofa window opening. Inorder to obtain a correct three dimensional viewing of the window in themasks, a spatial window image must appear out in front of the actualposition of the mask, i.e. between the eyes or viewing point and theclosest spatial object in the three dimensional scene. To accomplishthis there is provided by the invention a series of notches or embossedribs in the window frame opening, represented in FIG. 16 by thereference numerals 114, 116 and 118 for the left eye and 120, 122 and124 for the right eye. To obtain the sense of depth, the mask windowwill appear to the observer as being located approximately 3 to 4 feetin front of the film plane, because the rays from the eyes as they focuson various points of the stereo image are made to focus on the ribs ornotches also, (since the latter are in relatively the same plane as thefilm image) and such rays will spatially converge to form a vision inthe brain looking like an actual window in space, represented as 126 inFIG. 16. Thus, the rays passing through the left and right image ribs118 and will be made to converge at 128 at the window in space 126; therays passing along ribs 116 and 122 will converge at 130 and the rayspassing along ribs 118 and 124 will converge at 132. These ribs ornotches serve to provide definite points for the eyes to triangulateupon where otherwise there would be nothing but an unbroken horizontalline. Thus, the opportunity for the eyes to triangulate on pointsprovided by the ribs or notches in the relative center of the ratherwide window leaves no error in the data which the brain is provided.Therefore, there is no confusion and the brain causes the vision of thewindow to appear in space correctly at 126, where it is intended that itshould appear.

Since, in the case of thin metallic film masks such as 64 (discussed inconnection with FIGS. 6, 7, 8, 9 and 9a) there would be no surface uponwhich to provide a series of ribs, notches would be used to provide theeffeet just discussed. The application of notches to such a film mask isshown in FIG. 10 wherein a film mask 164, having the upper 116 and lower168 rails, and the upper 167 and lower 169 notches, is provided furtherwith the series of notches 176, 178 and on the lower edge of rail 166,and the series of notches 170, 172 and 174 on the upper edge of thelower rail 168. The two series of approximately V-shaped notches aresymmetrically located with respect to the window opening and as shown inFIG. 13, for example, are displaced to the left with respect to the maskcenter line.

I The mask shown in FIG. 13 would serve for viewing the right hand imageof the stereo pair since the ribs are displaced to the left. If used ininverted orientation then the mask of FIG. 13 would have the ribs beingdisplaced to the right of the physical center of the mask, and in thatposition the mask would then serve to hold the left hand image of thestereo pair.

Instead ofa thin metallic mask a plastic mask may be provided, as shownin FIGS. 11 through 15, inclusive. The mask 264 is formed with arelatively thicker upper 266 and lower 268 rails and the side flanges284 and 286. The upper edge of the upper rail 266 is provided with thenotch 267, and the lower edge of the lower rail 268 is provided with thenotch 269. In connection with the prior showing of the metal masks 64and 164 the notches at the outer edges of the rails extended completelythrough the thickness of the mask, because of the thin metal element.However, the use of plastic permits a thicker mask and the notches 267and 269 do not go entirely through the thickness of the mask. This isdesireable since in this manner the notches are hidden from theobserver. Because of their central location, the parallel rays from theeyes of the observer would tend to converge at a point of infinity, thuscausing confusion, if the notches or recesses were visable', theconfusion arising because the use of the ribs or notches on the innersurfaces of the rails would tend to cause the axis of the eyes toconverge at a point only several feet in front of the observer.

As shown in FIG. 13, the side flange 284 has a relatively narrower siderail 288 as compared with the side rail 290 of the side flange 286.Formed on the flange 288 are a pair of legs or feet 292 and 294; andsimilarly formed on the flange 286 are the legs or feet 296 and 298. Thelegs 292 and 294 are so oriented with respect to the legs 296 and 298that when inverted they will be presented in the same configuration topermit interchangeability of the mask from the right to the left side ofthe mount, and to especially provide that the legs on the right side ofthe left mask, and the left side of the right mask, do not interferewith each other when pressed into the common slot 46 in the center ofthe mount. The side flanges 284 and 286, together with the legs 292, 296and 298 serve the same function as the clips 92, 94, 96 and 98 describedin connection with mask 64. As shown in FIG. 14, the mask 264 is merelyplaced into the mount 1, with the flange 190 resting against the body 2and the leg 296 extending into the channel 42; and the leg 292 extendsinto the channel 46. Upon further assembly as shown in FIG. 15 the leg296 is seated into the channel 42 with its outer portion bearing againstthe inner wall ofthe ledge 38.

A series of ribs 300, 302 304 are provided on the upper edge of thelower rail 268; and a series of ribs, directly oppositely oriented, 306,308 and 310 are provided on the lower edge of the upper rail for thepurposes above described.

By placing the legs of the plastic mount, or the corresponding portionsof the clips in the case of the metal mount, into the channels 42, 44and 46 of the mount body 2, clearance is provided so that the alignmentof the mount in the viewer is not determined by any portion of the mask,but by the mount alone.

Although what has been described has been specific construction ofpreferred embodiments of the invention, it is to be understood thatvarious modifications and rearrangements of parts can be provided whilestill remaining within the spirit and scope of the appended claims.

What I claim is:

1. A film mount for a pair of panoramic stereoscopic images, comprising,in combination:

a body member;

said body member being provided with pairs of curved seats having adegree of curvature substantially corresponding to the focal radius ofacurved film bed upon which film is exposed to provide a pair ofpanoramic stereoscopic images;

a pair of window openings in said body member formed in part by saidpairs of curved seats;

and a pair of mask members provided with openings andadapted to bemounted within said window openings in said body member for holding andpositioning a pair of film frames bearing coordinate panoramicstereoscopic images, so that said images are viewable through said maskmembers openings.

2. The film mount of claim 1 wherein said body member and mask membersare provided with positively cooperating means for both vertical andhorizontal alignment of the mask members within said body member.

3. The film mount of claim 2 including stereo image film frame strips,one for each mask member, and means on said film frame stripscooperating with said positively cooperating means to position saidstrips upon their assembly with said mask members into said body membersin such manner that corresponding infimty image points on said stereofilm rames are located at a distance apart which is equal to the averageinterpupilary distance of the human eyes.

4. The film mount of claim 3 wherein said mask members are formed withmeans providing a plurality of reference points which are visible in theopenings therein, said means being so arranged as to cause an observerlooking through said stereo image film strips to focus his eyes on saidreference points at the same time that he views said images whereby thebrain will have no difficulty in causing to be formed a vision of thisopening located in space beyond the viewpoint but in front of theclosest spatial object appearing on the stereo image film frame strips.

5. The film mount of claim 2 wherein said mask members are soconstructed that said positively cooperating means are not visible tothe observer when viewing through the assembled film mount and maskmembers.

6. The film mount of claim 1 wherein said mask members are provided withmeans for assuring retention thereof within the body member, said lattermeans including a resilient element for simultaneously and fixedlyassembling'and retaining in position a film strip and a mask memberwithin said body.

7. The film mount of claim 6 wherein said body member is provided with aplurality of recesses, and said resilient means includes members soconstructed and arranged as to enter into said recesses and frictionallyengage a portion of walls thereof.

8. The film mount of claim 6 wherein said mask members are formed withcurved rails having a radius of curvature somewhat less than that intowhich they will be constrained upon installation into the mount, wherebyfollowing such installation pressure will be thereby applied to the filmstrips at the central area of their edges.

9. The film mount of claim 1 including means on said mask members whichare so constructed and arranged that upon assembly of the mask membersinto the body member the openings in said mask members are positioned tobe displaced slightly inwardly towards the vertical center of the bodymember by an amount which is slightly greater than the inwarddisplacement which the human eyes must accommodate when viewing close-upobjects, whereby there is then insured the visual formation of a spatialwindow in front of the plane in which said film strips lie when saidimages are viewed by an observer.

10. The film mount of claim 1 including retaining means formed on saidbody member for assuring proper alignment thereof in a viewer.

1. A film mount for a pair of panoramic stereoscopic images, comprising,in combination: a body member; said body member being provided withpairs of curved seats having a degree of curvature substantiallycorresponding to the focal radius of a curved film bed upon which filmis exposed to provide a pair of panoramic stereoscopic images; a pair ofwindow openings in said bOdy member formed in part by said pairs ofcurved seats; and a pair of mask members provided with openings andadapted to be mounted within said window openings in said body memberfor holding and positioning a pair of film frames bearing coordinatepanoramic stereoscopic images, so that said images are viewable throughsaid mask members openings.
 2. The film mount of claim 1 wherein saidbody member and mask members are provided with positively cooperatingmeans for both vertical and horizontal alignment of the mask memberswithin said body member.
 3. The film mount of claim 2 including stereoimage film frame strips, one for each mask member, and means on saidfilm frame strips cooperating with said positively cooperating means toposition said strips upon their assembly with said mask members intosaid body members in such manner that corresponding infinity imagepoints on said stereo film frames are located at a distance apart whichis equal to the average interpupilary distance of the human eyes.
 4. Thefilm mount of claim 3 wherein said mask members are formed with meansproviding a plurality of reference points which are visible in theopenings therein, said means being so arranged as to cause an observerlooking through said stereo image film strips to focus his eyes on saidreference points at the same time that he views said images whereby thebrain will have no difficulty in causing to be formed a vision of thisopening located in space beyond the viewpoint but in front of theclosest spatial object appearing on the stereo image film frame strips.5. The film mount of claim 2 wherein said mask members are soconstructed that said positively cooperating means are not visible tothe observer when viewing through the assembled film mount and maskmembers.
 6. The film mount of claim 1 wherein said mask members areprovided with means for assuring retention thereof within the bodymember, said latter means including a resilient element forsimultaneously and fixedly assembling and retaining in position a filmstrip and a mask member within said body.
 7. The film mount of claim 6wherein said body member is provided with a plurality of recesses, andsaid resilient means includes members so constructed and arranged as toenter into said recesses and frictionally engage a portion of wallsthereof.
 8. The film mount of claim 6 wherein said mask members areformed with curved rails having a radius of curvature somewhat less thanthat into which they will be constrained upon installation into themount, whereby following such installation pressure will be therebyapplied to the film strips at the central area of their edges.
 9. Thefilm mount of claim 1 including means on said mask members which are soconstructed and arranged that upon assembly of the mask members into thebody member the openings in said mask members are positioned to bedisplaced slightly inwardly towards the vertical center of the bodymember by an amount which is slightly greater than the inwarddisplacement which the human eyes must accommodate when viewing close-upobjects, whereby there is then insured the visual formation of a spatialwindow in front of the plane in which said film strips lie when saidimages are viewed by an observer.
 10. The film mount of claim 1including retaining means formed on said body member for assuring properalignment thereof in a viewer.